Physical Vapor Deposition System And Processes

ABSTRACT

A physical vapor deposition (PVD) chamber and a method of operation thereof are disclosed. Chambers and methods are described that provide a chamber comprising an upper shield with two holes that are positioned to permit alternate sputtering from two targets.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No.62/812,605, filed Mar. 1, 2019, the entire disclosure of which is herebyincorporated by reference herein.

TECHNICAL FIELD

The present disclosure relates generally to substrate processingsystems, and more specifically, embodiments pertain to physical vapordeposition systems with multiple cathode assemblies (multi-cathodes) andprocesses for physical vapor deposition.

BACKGROUND

Sputtering, alternatively called physical vapor deposition (PVD), isused for the deposition of metals and related materials in thefabrication of semiconductor integrated circuits. Use of sputtering hasbeen extended to depositing metal layers onto the sidewalls of highaspect-ratio holes such as vias or other vertical interconnectstructures, as well as in the manufacture of extreme ultraviolet (EUV)mask blanks. In the manufacture of EUV mask blanks, minimizing particlegeneration is desired, because particles negatively affect theproperties of the final product. Furthermore, in the manufacture of anEUV mask blank, a multilayer reflector comprising alternating layers ofdifferent materials, for example, silicon and molybdenum is deposited ina PVD chamber. Contamination of the individual silicon and molybdenumlayers caused by cross-contamination of the silicon and molybdenumtargets can be a problem which leads to EUV mask blank defects.

Plasma sputtering may be accomplished using either DC sputtering or RFsputtering. Plasma sputtering typically includes a magnetron positionedat the back of the sputtering target including at least two magnets ofopposing poles magnetically coupled at their back through a magneticyoke to project a magnetic field into the processing space to increasethe density of the plasma and enhance the sputtering rate from a frontface of the target. Magnets used in the magnetron are typically closedloop for DC sputtering and open loop for RF sputtering.

In plasma enhanced substrate processing systems, such as physical vapordeposition (PVD) chambers, high power density PVD sputtering with highmagnetic fields and high DC power can produce high energy at asputtering target, and cause a large rise in surface temperature of thesputtering target. The sputtering target is cooled by contacting atarget backing plate with cooling fluid. In plasma sputtering astypically practiced commercially, a target of the material to be sputterdeposited is sealed to a vacuum chamber containing the wafer to becoated. Argon is admitted to the chamber. In the sputtering processes,the sputtering target is bombarded by energetic ions, such as a plasma,causing material to be displaced from the target and deposited as a filmon a substrate placed in the chamber.

There remains a need to reduce defect sources such as particles andcross-contamination of targets of different material in a multi-cathodePVD chamber.

SUMMARY

In a first embodiment of the disclosure, a physical vapor deposition(PVD) chamber comprises a plurality of cathode assemblies including afirst cathode assembly including a first backing plate to support afirst target during a sputtering process and a second cathode assemblyincluding a second backing plate configured to support a second targetduring a sputtering process; an upper shield below the plurality ofcathode assemblies having a first shield hole having a diameter andpositioned on the upper shield to expose the first cathode assembly anda second shield hole having a diameter and positioned on the uppershield to expose the second cathode assembly, the upper shield having aflat inside surface, except for a region between the first shield holeand the second shield hole; and a raised area in the region between thefirst shield hole and the second shield hole, the raised area having aheight greater than one centimeter from the flat inside surface andhaving a length greater than the diameter of the first shield hole andthe diameter of the second shield hole, wherein the PVD chamber isconfigured to alternately sputter material from the first target and thesecond target without rotating the upper shield.

According to a second embodiment of the disclosure, a physical vapordeposition (PVD) chamber comprises a plurality cathode assembliesincluding a first cathode assembly including a first backing platesupporting a first target comprising molybdenum and a second cathodeassembly including a second backing plate supporting a second targetcomprising silicon, a third cathode assembly including a third backingplate supporting a third target comprising a dummy material, and afourth cathode assembly including a fourth backing plate supporting afourth target comprising a dummy material; an upper shield below theplurality of cathode assemblies having a first shield hole having adiameter and positioned on the upper shield to expose the first targetand a second shield hole having a diameter and positioned on the uppershield to expose the second target, the upper shield having a flatsurface, except for a region between the first shield hole and thesecond shield hole, the upper shield configured to permit molybdenum andsilicon material to be alternately sputtered from the first target andthe second target respectively without rotating the upper shield; and araised area in the region between the first shield hole and the secondshield hole, the raised area having a height greater than one centimeterand having a length greater than the diameter of the first shield holeand the second shield hole, wherein the upper shield is rotatable toallow one of the first shield hole and the second shield hole to exposethe first target and one of third target and the fourth target.

A third embodiment of the disclosure pertains to a method of depositingalternating material layers in a physical vapor deposition (PVD) chambercomprising: placing a substrate in the PVD chamber comprising aplurality cathode assemblies including a first cathode assemblyincluding a first target comprising a first material and a secondcathode assembly including a second target comprising a second materialdifferent from the first material. The method further comprisesdisposing an upper shield below the plurality of cathode assemblies, theupper shield having a first shield hole having a diameter and positionedon the upper shield to expose the first target and a second shield holehaving a diameter and positioned on the upper shield to expose thesecond target. The upper shield further comprises a flat surface betweenthe first shield hole and the second shield hole and a raised areabetween the two of the shield holes having a length at least equal tothe diameter of the first shield hole and the second shield hole. Themethod further comprises alternately sputtering material from the firsttarget and the second target without rotating the upper shield, whereinthe raised area prevents the first material from contaminating thesecond target and prevents the second material from contaminating thefirst target.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the presentdisclosure can be understood in detail, a more particular description ofthe disclosure, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this disclosure and are therefore not to beconsidered limiting of its scope, for the disclosure may admit to otherequally effective embodiments.

FIG. 1 is a side view of a prior art deposition system;

FIG. 2 is a side view of a PVD chamber according to one or moreembodiments;

FIG. 3 is a bottom isometric view of the upper shield of the PVD chamberof FIG. 2;

FIG. 4A is bottom view of the upper shield and targets in a firstrotational position;

FIG. 4B is a bottom view of the upper shield and the targets in a secondrotational position; and

FIG. 4C is a bottom view of the upper shield and the targets in a thirdrotational position.

DETAILED DESCRIPTION

Before describing several exemplary embodiments of the disclosure, it isto be understood that the disclosure is not limited to the details ofconstruction or process steps set forth in the following description.The disclosure is capable of other embodiments and of being practiced orbeing carried out in various ways.

As used in this specification and the appended claims, the term“substrate” refers to a surface, or portion of a surface, upon which aprocess acts. It will also be understood by those skilled in the artthat reference to a substrate can also refer to only a portion of thesubstrate, unless the context clearly indicates otherwise. Additionally,reference to depositing on a substrate can mean both a bare substrateand a substrate with one or more films or features deposited or formedthereon

A “substrate” as used herein, refers to any substrate or materialsurface formed on a substrate upon which film processing is performedduring a fabrication process. For example, a substrate surface on whichprocessing can be performed include materials such as silicon, siliconoxide, strained silicon, silicon on insulator (SOI), carbon dopedsilicon oxides, amorphous silicon, doped silicon, germanium, galliumarsenide, glass, sapphire, and any other materials such as metals, metalnitrides, metal alloys, and other conductive materials, depending on theapplication. Substrates include, without limitation, semiconductorwafers. Substrates may be exposed to a pretreatment process to polish,etch, reduce, oxidize, hydroxylate, anneal, UV cure, e-beam cure and/orbake the substrate surface. In addition to film processing directly onthe surface of the substrate itself, in the present disclosure, any ofthe film processing steps disclosed may also be performed on anunderlayer formed on the substrate as disclosed in more detail below,and the term “substrate surface” is intended to include such underlayeras the context indicates. Thus, for example, where a film/layer orpartial film/layer has been deposited onto a substrate surface, theexposed surface of the newly deposited film/layer becomes the substratesurface.

The term “horizontal” as used herein is defined as a plane parallel tothe plane or surface of a mask blank, regardless of its orientation. Theterm “vertical” refers to a direction perpendicular to the horizontal asjust defined. Terms, such as “above”, “below”, “bottom”, “top”, “side”(as in “sidewall”), “higher”, “lower”, “upper”, “over”, and “under”, aredefined with respect to the horizontal plane, as shown in the figures.

The term “on” indicates that there is direct contact between elements.The term “directly on” indicates that there is direct contact betweenelements with no intervening elements.

Those skilled in the art will understand that the use of ordinals suchas “first” and “second” to describe process regions do not imply aspecific location within the processing chamber, or order of exposurewithin the processing chamber.

Embodiments of the disclosure pertain to a magnet design for adeposition system, for example a physical vapor deposition (“PVD”)chamber comprising at least one cathode assembly, and in particularembodiments, a PVD chamber comprising multiple cathode assemblies(referred to herein as a “multi-cathode chamber).

FIG. 1 shows a prior art PVD system, in which a side view of a portionof a deposition system in the form of a PVD chamber 100 is shown. Thedeposition system in the form of a PVD chamber is shown as amulti-cathode PVD chamber 100 including a plurality of cathodeassemblies 102. The multi-cathode PVD chamber 100 is shown as includinga multi-target PVD source configured to manufacture an MRAM(magnetoresistive random access memory) or a multi-target PVD sourceconfigured to manufacture an extreme ultraviolet (EUV) mask blank, forexample a target comprising silicon and a target comprising molybdenumto form a multilayer stack reflective of EUV light.

The multi-cathode PVD chamber comprises a chamber body 101, comprisingan adapter (not shown) configured to hold a plurality of cathodeassemblies 102 in place in a spaced apart relationship. Themulti-cathode PVD chamber 100 can include a plurality of cathodeassemblies 102 for PVD and sputtering. Each of the cathode assemblies102 is connected to a power supply 112, including direct current (DC)and/or radio frequency (RF).

The cross-sectional view depicts an example of a PVD chamber 100including the chamber body 101 defining an inner volume 121, where asubstrate or carrier is processed. The cathode assemblies 102 in theembodiment shown in FIG. 1 can be used for sputtering differentmaterials as a material layer 103. The cathode assemblies 102 exposedthrough shield holes 104 of an upper shield 106, which is disposed overthe substrate or carrier 108 on a rotating pedestal 110. The uppershield 106 is generally conical in shape. There may generally be onlyone carrier 108 over or on the rotating pedestal 110.

The substrate or carrier 108 is shown as a structure having asemiconductor material used for fabrication of integrated circuits. Forexample, the substrate or carrier 108 comprises a semiconductorstructure including a wafer. Alternatively, the substrate or carrier 108can be another material, such as an ultra low expansion glass substrateused to form an EUV mask blank. The substrate or carrier 108 can be anysuitable shape such as round, square, rectangular or any other polygonalshape.

The upper shield 106 is formed with the shield holes 104 so that thecathode assemblies 102 can be used to deposit the material layers 103through the shield holes 104. A power supply 112 is applied to thecathode assemblies 102. The power supply 112 can include a directcurrent (DC) or radio frequency (RF) power supply.

The upper shield 106 is configured to expose one of the cathodeassemblies 102 at a time and protect other cathode assemblies 102 fromcross-contamination. The cross-contamination is a physical movement ortransfer of a deposition material from one of the cathode assemblies 102to another of the cathode assemblies 102. The cathode assemblies 102 arepositioned over targets 114. A design of a chamber can be compact. Thetargets 114 can be any suitable size. For example, each of the targets114 can be a diameter in a range of from about 4 inches to about 20inches, or from about 4 inches to about 15 inches, or from about 4inches to about 10 inches, or from about 4 inches to about 8 inches orfrom about 4 inches to about 6 inches.

In FIG. 1, the substrate or carrier 108 is shown as being on therotating pedestal 110, which can vertically move up and down. Before thesubstrate or carrier 108 moves out of the chamber, the substrate orcarrier 108 can move below a lower shield 118. A telescopic cover ring120 abuts the lower shield 118. Then, the rotating pedestal 110 can movedown, and then the carrier 108 can be raised with a robotic arm beforethe carrier 108 moves out of the chamber.

When the material layers 103 are sputtered, the materials sputtered fromthe targets 114 can be retained inside and not outside of the lowershield 118. In this prior art embodiment, telescopic cover ring 120includes a raised ring portion 122 that curves up and has a predefinedthickness. The telescopic cover ring 120 can also include a predefinedgap 124 and a predefined length with respect to the lower shield 118.Thus, the materials that form material layers 103 will not be below therotating pedestal 110 thereby eliminating contaminants from spreading tothe substrate or carrier 108.

FIG. 1 depicts individual shrouds 126. The shrouds 126 can be designedsuch that a majority of the materials from the targets 114 that does notdeposit on the carrier 108 is contained in the shrouds 126, hence makingit easy to reclaim and conserve the materials. This also enables one ofthe shrouds 126 for each of the targets 114 to be optimized for thattarget to enable better adhesion and reduced defects.

The shrouds 126 can be designed to minimize cross-talk or cross-targetcontamination between the cathode assemblies 102 and to maximize thematerials captured for each of the cathode assemblies 102. Therefore,the materials from each of the cathode assemblies 102 would just beindividually captured by one of the shrouds 126 over which the cathodeassemblies 102 are positioned. The captured materials may not bedeposited on the substrate or carrier 108. For example, a first cathodeassembly and a second cathode assembly can apply alternating layers ofdifferent materials in the formation of an extreme ultraviolet maskblank, for example, alternating layers of silicon deposited from a firsttarget and cathode assembly 102 and a molybdenum from a second targetand cathode assembly 102.

The substrate or carrier 108 can be coated with uniform material layer103 deposited on a surface of the substrate or carrier 108 using thedeposition materials including a metal from the targets 114 over theshrouds 126. Then, the shrouds 126 can be taken through a recoveryprocess. The recovery process not only cleans the shrouds 126 but alsorecovers a residual amount of the deposition materials remained on or inthe shrouds 126. For example, there may be molybdenum on one of theshrouds 126 and then silicon on another of the shrouds 126. Sincemolybdenum is more expensive than silicon, the shrouds 126 withmolybdenum can be sent out for the recovery process.

As shown in FIG. 1, the lower shield 118 is provided with a first bendresulting from small angle 130 and a second bend resulting from largeangle 132, which result in a knee 119 in the lower shield 118. This knee119 provides an area in which particles can accumulate duringdeposition, and is thus a possible source for processing defects.

PVD chambers and processes are utilized to manufacture extremeultraviolet (EUV) mask blanks. An EUV mask blank is an optically flatstructure used for forming a reflective mask having a mask pattern. Thereflective surface of the EUV mask blank forms a flat focal plane forreflecting the incident light, such as the extreme ultraviolet light. AnEUV mask blank comprises a substrate providing structural support to anextreme ultraviolet reflective element such as an EUV reticle. Thesubstrate is made from a material having a low coefficient of thermalexpansion (CTE) to provide stability during temperature changes, forexample, a material such as silicon, glass, oxides, ceramics, glassceramics, or a combination thereof.

Extreme ultraviolet (EUV) lithography, also known as soft x-rayprojection lithography, can be used for the manufacture of 0.0135 micronand smaller minimum feature size semiconductor devices. However, extremeultraviolet light, which is generally in the 5 to 100 nanometerwavelength range, is strongly absorbed in virtually all materials. Forthat reason, extreme ultraviolet systems work by reflection rather thanby transmission of light. Through the use of a series of mirrors, orlens elements, and a reflective element, or a mask blank, coated with anon-reflective absorber mask pattern, the patterned actinic light isreflected onto a resist-coated semiconductor substrate.

The lens elements and mask blanks of extreme ultraviolet lithographysystems are coated with reflective multilayer stack of coatings ofalternating reflective layers of materials such as molybdenum andsilicon. Reflection values of approximately 65% per lens element or maskblank have been obtained by using substrates that are coated withmultilayer coatings that strongly reflect extreme ultraviolet lightwithin an extremely narrow ultraviolet bandpass, for example, 12.5 to14.5 nanometer bandpass for 13.5 nanometer ultraviolet light. During themanufacture of EUV mask blanks and lens elements, minimization ofdefects such as defects from particle sources and high reflectivity ofthe reflective multilayer stack are generally desired.

FIG. 2 depicts a PVD chamber 200 in accordance with a first embodimentof the disclosure. PVD chamber 200 includes a plurality of cathodeassemblies 202 a and 202 b. While only two cathode assemblies 202 a and202 b are shown in the side view of FIG. 2, a multicathode chamber cancomprise more than two cathode assemblies, for example, five, six ormore than six cathode assemblies. An upper shield 206 is provided belowthe plurality of cathode assemblies 202 a and 202 b, the upper shield206 having two shield holes 204 a and 204 b to expose targets 205 a, 205b disposed at the bottom of the cathode assemblies 202 a to the interiorspace 221 of the PVD chamber 200. A middle shield 216 is provided belowand adjacent upper shield 206, and a lower shield 218 is provided belowand adjacent upper shield 206.

A modular chamber body is disclosed in FIG. 2, in which an intermediatechamber body 225 is located above and adjacent a lower chamber body 227.The intermediate chamber body 225 is secured to the lower chamber body227 to form the modular chamber body, which surrounds lower shield 218and the middle shield. A top adapter lid 273 (shown in FIG. 8) isdisposed above intermediate chamber body 225 to surround upper shield206.

PVD chamber 200 is also provided with a rotating pedestal 210 similar torotating pedestal 110 in FIG. 1. A person of ordinary skill will readilyappreciate that other components of a PVD chamber, such as thosereferenced above in FIG. 1 but omitted in FIG. 2 for the sake ofclarity, are provided in PVD chamber 200 according to one or moreembodiments. It will be appreciated that the upper shield 206 of the PVDchamber 200 of FIG. 2 is substantially flat, compared to the conicalupper shield 106 of FIG. 1.

Thus, a first aspect of the disclosure pertains to a PVD chamber 200,which comprises a plurality cathode assemblies including a first cathodeassembly 202 a including a first backing plate 210 a configured tosupport a first target 205 a during a sputtering process and a secondcathode assembly 202 b including a second backing plate 210 b configuredto support a second target 205 b during a sputtering process. The PVDchamber further comprises an upper shield 206 below the plurality ofcathode assemblies 202 a, 202 b having a first shield hole 204 a havinga diameter D1 and positioned on the upper shield to expose the firstcathode assembly 202 a and a second shield hole 204 b having a diameterD2 and positioned on the upper shield 206 to expose the second cathodeassembly 202 b, the upper shield 206 having a substantially flat insidesurface 203, except for a region 207 between the first shield hole 204 aand the second shield hole 204 b.

The upper shield 206 includes a raised area 209 in the region 207between the first shield hole and the second shield hole, the raisedarea 209 having a height “H” from the substantially flat inside surface203 that greater than one centimeter from the flat inside surface 203(best seen in FIG. 1) and having a length “L” greater than the diameterD1 of the first shield hole 204 a and the diameter D2 of the secondshield hole 204 b, wherein the PVD chamber is configured to alternatelysputter material from the first target 205 a and the second target 205 bwithout rotating the upper shield 206.

In one or more embodiments, the raised area 209 has a height H so thatduring a sputtering process, the raised area height H is sufficient toprevents material sputtered from the first target 205 a from beingdeposited on the second target 205 b and to prevent material sputteredfrom the second target 205 b from being deposited on the first target205 a.

According to one or more embodiments of the disclosure, the firstcathode assembly 202 a comprises a first magnet spaced apart from thefirst backing plate 210 a at a first distance d1 and the second cathodeassembly 202 b comprises a second magnet 220 b spaced apart from thesecond backing plate 210 b at a second distance d2, wherein the firstmagnet 220 a and the second magnet 220 b are movable such that the firstdistance d1 can be varied (as indicated by arrow 211 a) and the seconddistance d2 can be varied (as indicated by arrow 211 b. The distance d1and the distance d2 can be varied by linear actuator 213 a to change thedistance d1 and linear actuator 213 b to change the distance d2. Thelinear actuator 213 a and the linear actuator 213 b can comprise anysuitable device that can respectively effect linear motion of firstmagnet assembly 215 a and second magnet assembly 215 b. First magnetassembly 215 a includes rotational motor 217 a, which can comprise aservo motor to rotate the first magnet 220 a via shaft 219 a coupled torotational motor 217 a. Second magnet assembly 215 b includes rotationalmotor 217 b, which can comprise a servo motor to rotate the secondmagnet 220 b via shaft 219 b coupled to rotational motor 217 b. It willbe appreciated that the first magnet assembly 215 a may include aplurality of magnets in addition to the first magnet 220 a. Similarly,the second magnet assembly 215 b may include a plurality of magnets inaddition to the second magnet 220 b.

In one or more embodiments, wherein the first magnet 220 a and secondmagnet 220 b are configured to be moved to decrease the first distanced1 and the second distance d2 to increase magnetic field strengthproduced by the first magnet 220 a and the second magnet 220 b and toincrease the first distance d1 and the second distance d2 to decreasemagnetic field strength produced by the first magnet 220 a and thesecond magnet 220 b.

In some embodiments, the first target 205 a comprises a molybdenumtarget and the second target 205 b comprises a silicon target, and thePVD chamber 200 further comprises a third cathode assembly (not shown)including a third backing plate to support a third target 205 c (seeFIGS. 4A-C) and a fourth cathode assembly (not shown) including a fourthbacking plate configured to support a fourth target 205 d (see FIGS.4A-C). The third cathode assembly and fourth cathode assembly accordingto one or more embodiments are configured in the same manner as thefirst and second cathode assemblies 202 a, 202 b as described herein. Insome embodiments, the third target 205 c comprises a dummy target andthe fourth target 205 d comprises a dummy target. As used herein, “dummytarget” refers to a target that is not intended to be sputtered in thePVD apparatus 200.

Referring now to FIGS. 4A-C, the first target 205 a, the second target205 b, the third target 205 c and the fourth target 205 d are positionedwith respect to each other and the first shield hole 204 a and secondshield hold 204 b so that. In the embodiment shown, first target(positioned under first cathode assembly 202 a) is at position P1, thesecond target 205 b (positioned under second cathode assembly 202 b) isat position P2. In some embodiments, the raised area 209 is positionedbetween first shield hold 204 a and second shield hole 204 b. In theembodiment shown, the first shield hole 204 a and the second shield hole204 b are positioned with respect to the first target 205 a, the secondtarget 205 b, the third target 205 c and the fourth target 205 d tofacilitate cleaning of the first target 205 a and the second target 205b.

In use, the PVD chamber according to one or more embodiments operates asfollows during a deposition process. The first shield hole 204 a ispositioned to expose the first target, and the second shield hole 204 bis positioned to expose the second target 205 b. The first target 205 aand the second target 205 b are comprised of different materials. In aspecific embodiment of the disclosure, the first target 205 a comprisesmolybdenum and the second target 205 b comprises silicon. During adeposition process, material is alternately sputtered from the firsttarget 205 a and the second target 205 b to form a multilayer stack ofalternating materials layers where adjacent layers comprise differentmaterials. Deposition of the alternating layers of materials from thefirst target 205 a and the second target 205 b occurs without rotatingthe upper shield 206, which reduces generation of particulate comparedto an apparatus with a single shield hole in which the upper shield mustbe rotated to accomplish alternate deposition of different materials toform a multilayer stack comprised of two different materials. In one ormore embodiments, the alternating layers comprise silicon and molybdenumto form a multilayer stack that is reflective of EUV light. FIG. 4Adepicts the position of the first target 205 a in position P1 and target205 b at position P2. In some embodiments, the upper shield comprises araised area 209 in the region 207 between the first shield hold 204 aand the second shield hole 204 b.

In the embodiment shown, the upper shield 206 is circular, and thecenter of the first shield hole 204 a at the first position P1, and thesecond position P2 where the center of the second shield hole 204 b islocated is 150 degrees in a counterclockwise direction indicated byarrow 261 from the center of the first shield hole 204 a. Likewise, thecenter of target 205 a and the center 205 b at positions P1 and P2,which are 150 degrees apart from each other. In FIG. 4A third target 205c and fourth target 205 d are dummy targets, which are covered by theflat surface of the upper shield 206 and shown with their outlines asdotted lines.

FIG. 4B shows the position of the first shield hold 204 a as positionedover second target 205 b and the second shield hold 204 b as positionedover fourth target 205 d, which is a dummy target. The shield holes 204a and 204 b have been rotated counterclockwise 150 degrees from thedeposition position of FIG. 4A. The position of the first shield hole atposition P4 is over the fourth target 205 d, the center of which islocated 300 degrees counterclockwise from the center of the first target205 a. The second shield hole 204 b is now located over the secondtarget 205 b, the center of which is located 150 degreescounterclockwise from the center of the first target 205 a. It will beunderstood by a person of ordinary skill in the art that the positionsof the individual targets are fixed with respect to their respectivecathode assemblies, while the upper shield 206 is rotated over thetargets. FIG. 4B is a cleaning position, in which the second target 205b can be cleaned using a plasma. An advantage of cleaning in the mannershows in FIG. 4B where the second shield hole 204 b is positioned toexpose a dummy target (fourth target 205 d) while the first shield holeexposes the second target 205 b is that cleaning of the second targetcan be conducted while the first target 205 a is covered (as indicatedby the dashed line), and the first target 205 a will not be contaminatedby the cleaning process which removes contaminants from the secondtarget, which is a different material from the first target. Inaddition, the fourth target 205 d, which is a dummy target prevents thematerial which has been cleaned from the second target 205 b fromtravelling through an open shield hole (the second shield hole 204 b)and contaminating the chamber, namely the top adapter lid 273.

FIG. 4C shows the position of the shield holes 204 a and 204 b afterrotation counterclockwise 60 degrees, as indicated by arrow 260 in FIG.4B. In this position, the second shield hole, which has now been rotated210 degrees from the deposition position shown in FIG. 4A is nowpositioned over the first target 205 a at position P1, and the firstshield hole 204 a is now positioned over the third target 205 c, whichis a dummy target. The second target 205 b and the fourth target 205 d,both shown as dashed lines, are now covered by the upper shield. In theposition shown in FIG. 4C, the first target 205 a is exposed through thesecond shield hole 204 b and the third target 205 c is exposed by thefirst shield hole 204 a. The first target 205 a can be cleaned in acleaning process with a plasma

Summarizing FIGS. 4A-C, by spacing electrode assemblies and theassociated targets at the periphery of a multicathode chamber in themanner shown and using a rotatable upper shield comprising two shieldholes spaced from each other at the periphery of the upper shield asshown, the first target 205 a and the second target 205 b can be cleanedusing a plasma process in a PVD chamber. In one or more embodiments,when the third target 205 c and the fourth target 205 d are dummytargets that are not intended to be sputtered as part of depositionprocess, the dummy targets prevent contamination of the chamber duringcleaning of the first target 205 a and the second target 205 b. In someembodiments, the dummy targets comprise a side and front surface (thesurface facing the PVD chamber and substrate in the PVD chamber) aretextured to ensure no particle generation after large amount ofdeposition of material which has been cleaned from the first target 205a and the second target 205 b. In some embodiments, the textured surfaceis provided by arc spraying.

In the specific embodiment shown, the upper shield 206 is circular, andtwo shield holes are spaced at the outer periphery of the upper shield206 at the shield hole centers so that when the upper shield 206 isrotated with respect to the PVD chamber 200, the shield holes expose twotargets (either deposition targets such as first target 205 a and thesecond target 205 b). The first shield hold 204 a and the second shieldhole are spaced apart by their centers by 150 degrees on the outerperiphery of the upper shield 206, and indicated by arrow 261 in FIG.4A.

In the embodiment shown, at least four cathode assemblies and targetsbelow the cathode assemblies are spaced around the outer periphery ofthe of PVD chamber top adapter lid 273 so that when the upper shield 206is rotated, two different targets are exposed each time the upper shieldis rotated. In FIGS. 4A-C, the center of second target 205 b, which iscircular, is 150 degrees in a counterclockwise direction from the centerof the first target 205 a, which is also circular. Additionally, thecenter of third target 205 c, which is circular and a dummy target is210 degrees in a counterclockwise direction from the center of the firsttarget 205 a, and the center of fourth target 205 d, which is circularand a dummy target is 300 degrees in a counterclockwise direction fromthe first target. By arranging the targets in this manner on the topadapter lid 273 and the upper shield 206 having the centers of theshield holes 204 a and 204 b spaced apart by 250 degrees, but rotatingthe upper shield 206, the first and second targets 205 a, 205 b can bothbe exposed during a deposition process, and then during a cleaningprocess the second target 205 b and a dummy target can be exposed toclean the second target and the first target 205 a and another dummytarget can be exposed to clean the first target 205 a while the otherdeposition target is not subject to contamination from cleaning of thetarget.

Stated another way, in one or more embodiments, the third target 205 cand the fourth target 205 d are positioned with respect to the firsttarget 205 a and second target 205 b so that when the upper shield 206is in a first position, the first target 205 a is exposed through thefirst shield hole 204 a and the second target 205 b is exposed throughthe second shield hole 204 b, and the third target 205 c and fourthtarget 205 d are covered by the upper shield 206. When the upper shield206 is rotated to a second position, the fourth target 205 d is exposedthrough the second shield hole 204 b and the second target 205 b isexposed through the first shield hole 204 a. In some embodiments, whenthe upper shield 206 is rotated to a third position, the first target205 is exposed through the second shield hole 204 b and the fourthtarget 205 d is exposed through the first shield hole 204 a.

In another embodiment, a physical vapor deposition (PVD) chamber 200comprises a plurality cathode assemblies including a first cathodeassembly 202 a including a first backing plate 210 a supporting a firsttarget 205 a comprising molybdenum and a second cathode assembly 202 bincluding a second backing plate 210 b supporting a second target 205 bcomprising silicon, a third cathode assembly including a third backingplate supporting a third target 205 c comprising a dummy material, and afourth cathode assembly including a fourth backing plate supporting afourth target 205 d comprising a dummy material. In this embodiment, anupper shield 206 is below the plurality of cathode assemblies having afirst shield hole 204 a having a diameter D and positioned on the uppershield to expose the first target 205 a and a second shield hole 204 bhaving a diameter D and positioned on the upper shield to expose thesecond target 205, the upper shield 206 having a flat surface 203between the first shield hole 204 a and the second shield hole 204 b andconfigured to permit molybdenum and silicon material to be alternatelysputtered from the first target 205 a and the second target 205 brespectively without rotating the upper shield 206. In this embodiment,the upper shield 206 includes a raised area 207 between the two of theshield holes having a height H greater than one centimeter and having alength greater than the diameter D of the first shield hole 204 a andthe second shield hole 204 b, wherein the upper shield 206 is rotatableto allow one of the first shield hole 204 a and the second shield hole204 b to expose the first target 205 a and one of third target 205 c andthe fourth target 205 d.

In some embodiments, each of the first cathode assembly, the secondcathode assembly, third cathode assembly and fourth cathode assemblycomprise a magnet spaced apart from the first backing plate at a firstdistance, the second backing plate at a second distance, the thirdbacking plate at a third distance and the fourth backing plate at afourth distance, each of the magnets being movable to increase ordecrease each of the first distance, the second distance, third distanceor fourth distance. Decreasing the first distance, the second distance,the third distance or the fourth distance increases magnetic fieldstrength produced by the magnet. Increasing the first distance, thesecond distance, the third distance or the fourth distance decreasesmagnetic field strength produced by the magnet.

Plasma sputtering may be accomplished using either DC sputtering or RFsputtering in the PVD chamber 200. In some embodiments, the processchamber includes a feed structure for coupling RF and DC energy to thetargets associated with each cathode assembly. For cathode assembly 202a, a first end of the feed structure can be coupled to an RF powersource 248 a and a DC power source 250 a, which can be respectivelyutilized to provide RF and DC energy to the target 205 a. The RF powersource 248 a is coupled to RF power in 249 a and the DC power source 250a is coupled to DC power in 251 a. For example, the DC power source 250a may be utilized to apply a negative voltage, or bias, to the target305 a. In some embodiments, RF energy supplied by the RF power source248 a may range in frequency from about 2 MHz to about 60 MHz, or, forexample, non-limiting frequencies such as 2 MHz, 13.56 MHz, 27.12 MHz,40.68 MHz or 60 MHz can be used. In some embodiments, a plurality of RFpower sources may be provided (i.e., two or more) to provide RF energyin a plurality of the above frequencies.

Likewise, for cathode assembly 202 b, a first end of the feed structurecan be coupled to an RF power source 248 b and a DC power source 250 b,which can be respectively utilized to provide RF and DC energy to thetarget 205 b. The RF power source 248 b is coupled to RF power in 249 aand the DC power source 250 b is coupled to DC power in 251 b. Forexample, the DC power source 250 b may be utilized to apply a negativevoltage, or bias, to the target 305 b. In some embodiments, RF energysupplied by the RF power source 248 b may range in frequency from about2 MHz to about 60 MHz, or, for example, non-limiting frequencies such as2 MHz, 13.56 MHz, 27.12 MHz, 40.68 MHz or 60 MHz can be used. In someembodiments, a plurality of RF power sources may be provided (i.e., twoor more) to provide RF energy in a plurality of the above frequencies.

While the embodiment shown includes separate RF power sources 248 a and248 b for cathode assemblies 202 a and 202 b, and separate DC powersources 250 a and 250 b for cathode assemblies 202 a and 202 b, the PVDchamber can comprise a single RF power source and a single DC powersource with feeds to each of the cathode assemblies.

Another aspect of the disclosure pertains to a method of depositingalternating material layers in a physical vapor deposition (PVD)chamber. In one embodiment, the method comprises placing a substrate 270in the PVD chamber 200 comprising a plurality cathode assembliesincluding a first cathode assembly 202 a including a first target 205 acomprising a first material and a second cathode assembly 202 bincluding a second target 205 b comprising a second material differentfrom the first material. The method further comprises disposing an uppershield 206 below the plurality of cathode assemblies, the upper shieldhaving a first shield hole 204 a having a diameter D1 and positioned onthe upper shield 206 to expose the first target 205 a and a secondshield hole 204 b having a diameter D2 and positioned on the uppershield 206 to expose the second target 205 b, the upper shield 206further comprising a flat surface 203 between the first shield hole 204a and the second shield hole 204 b and a raised area 209 in a region 207between the two of the shield holes 204 a, 204 b having a length L atleast equal to the diameter D1 of the first shield hole and the secondshield hole D2. In some embodiments, the raised area 207 has a height Hgreater than one centimeter. The method further comprises alternatelysputtering material from the first target 204 a and the second target204 b without rotating the upper shield 206, wherein the raised areaprevents the first material from contaminating the second target andprevents the second material from contaminating the first target.

In some embodiments of the method, the PVD chamber further comprises athird target 205 c comprising dummy material and a fourth target 205 dcomprising dummy material and wherein third target 205 c and the fourthtarget 205 d are positioned with respect to the first target 205 a andsecond target 205 b so that when the upper shield 206 is in a firstposition, the first target 205 a is exposed through the first shieldhole 204 a and the second target 205 b is exposed through the secondshield hole 204 b, and the third target 205 c and fourth target 205 dare covered by the upper shield 206 during depositing alternatingmaterial layers from the first target 205 a and the second target 205 b.

In some embodiments of the method, the method further comprises cleaningfirst material deposited on the second target 205 b by applying amagnetic field to the second target that is greater than a magneticfield applied during depositing alternating material layers. In someembodiments, the method further comprises comprising cleaning secondmaterial deposited on the first target 205 a by applying a magneticfield to the first target that 205 a is greater than a magnetic fieldapplied during depositing alternating material layers.

In some embodiments, the method further comprises rotating the uppershield 206 from the first position to a second position prior tocleaning the first material from the second target 205 b, the fourthtarget 205 d is exposed through the second shield hole 204 b and thesecond target 205 b is exposed through the first shield hole 204 a. Inone or more embodiments, the method comprises rotating the upper shield206 from the second position to a third position so that the firsttarget 205 a is exposed through the second shield hole 204 b and thefourth target 205 d is exposed through the first shield hole 204 a. Inspecific embodiments of the method, the substrate 270 comprises anextreme ultraviolet (EUV) mask blank. In specific embodiments of themethod the first target material comprises molybdenum and the secondtarget material comprises silicon. In some embodiments, the methodfurther comprises depositing multiple alternating materials layerscomprising a first layer comprising molybdenum and a second layercomprising silicon.

A benefit of the upper shield with the first shield hole 204 a and thesecond shield hole arranged in the upper shield according to embodimentsdescribed herein include the ability to deposit alternating layers ofdifferent materials without rotating the upper shield. In someembodiments, after completion of a process of depositing a multilayerstack on a substrate, the upper shield can be rotated as described aboveto conduct a cleaning operation in which one of the shield holes ispositioned over a dummy target.

In some embodiments, the methods described are conducted in the PVDchamber 200 by using a controller 290. There may be a single controlleror multiple controllers. When there is more than one controller, each ofthe controllers is in communication with each of the other controllersto control of the overall functions of the PVD chamber 200. For example,when multiple controllers are utilized, a primary control processor iscoupled to and in communication with each of the other controllers tocontrol the system. The controller is one of any form of general-purposecomputer processor, microcontroller, microprocessor, etc., that can beused in an industrial setting for controlling various chambers andsub-processors. As used herein, “in communication” means that thecontroller can send and receive signals via a hard-wired communicationline or wirelessly.

Each controller can comprise processor 292, a memory 294 coupled to theprocessor, input/output devices coupled to the processor 292, andsupport circuits 296 and 298 to provide communication between thedifferent electronic components. The memory includes one or more oftransitory memory (e.g., random access memory) and non-transitory memory(e.g., storage) and the memory of the processor may be one or more ofreadily available memory such as random access memory (RAM), read-onlymemory (ROM), floppy disk, hard disk, or any other form of digitalstorage, local or remote. The memory can retain an instruction set thatis operable by the processor to control parameters and components of thesystem. The support circuits are coupled to the processor for supportingthe processor in a conventional manner. Circuits may include, forexample, cache, power supplies, clock circuits, input/output circuitry,subsystems, and the like.

Processes may generally be stored in the memory as a software routinethat, when executed by the processor, causes the process chamber toperform processes of the present disclosure. The software routine mayalso be stored and/or executed by a second processor that is remotelylocated from the hardware being controlled by the processor. In one ormore embodiments, some or all of the methods of the present disclosureare controlled hardware. As such, in some embodiments, the processes areimplemented by software and executed using a computer system, inhardware as, e.g., an application specific integrated circuit or othertype of hardware implementation, or as a combination of software andhardware. The software routine, when executed by the processor,transforms the general purpose computer into a specific purpose computer(controller) that controls the chamber operation such that the processesare performed.

In some embodiments, the controller has one or more configurations toexecute individual processes or sub-processes to perform the method. Insome embodiments, the controller is connected to and configured tooperate intermediate components to perform the functions of the methods.

The PVD chambers 200 and methods described herein may be particularlyuseful in the manufacture of extreme ultraviolet (EUV) mask blanks. AnEUV mask blank is an optically flat structure used for forming areflective mask having a mask pattern. In one or more embodiments, thereflective surface of the EUV mask blank forms a flat focal plane forreflecting the incident light, such as the extreme ultraviolet light. AnEUV mask blank comprises a substrate providing structural support to anextreme ultraviolet reflective element such as an EUV reticle. In one ormore embodiments, the substrate is made from a material having a lowcoefficient of thermal expansion (CTE) to provide stability duringtemperature changes. The substrate according to one or more embodimentsis formed from a material such as silicon, glass, oxides, ceramics,glass ceramics, or a combination thereof.

An EUV mask blank includes a multilayer stack, which is a structure thatis reflective to extreme ultraviolet light. The multilayer stackincludes alternating reflective layers of a first reflective layer and asecond reflective layer. The first reflective layer and the secondreflective layer form a reflective pair. In a non-limiting embodiment,the multilayer stack includes a range of 20-60 of the reflective pairsfor a total of up to 120 reflective layers.

The first reflective layer and the second reflective layer can be formedfrom a variety of materials. In an embodiment, the first reflectivelayer and the second reflective layer are formed from silicon andmolybdenum, respectively. The multilayer stack forms a reflectivestructure by having alternating thin layers of materials with differentoptical properties to create a Bragg reflector or mirror. Thealternating layer of, for example, molybdenum and silicon are formed byphysical vapor deposition, for example, in a multi-cathode sourcechamber as described herein. In one or more embodiments, the chambersand the methods described herein can be used to deposit a multilayerstack of 20-60 reflective pairs of molybdenum and silicon. The uniquestructure of the upper shield with two shield holes enables depositionof a multilayer stack with fewer defects. The multicathode arrangementwith the targets including the dummy targets as arranged in theembodiments described herein facilitates cleaning of the molybdenum andsilicon targets.

The PVD chambers 200 described herein are utilized to form themultilayer stack, as well as capping layers and absorber layers. Forexample, the physical vapor deposition systems can form layers ofsilicon, molybdenum, titanium oxide, titanium dioxide, ruthenium oxide,niobium oxide, ruthenium tungsten, ruthenium molybdenum, rutheniumniobium, chromium, tantalum, nitrides, compounds, or a combinationthereof. Although some compounds are described as an oxide, it isunderstood that the compounds can include oxides, dioxides, atomicmixtures having oxygen atoms, or a combination thereof.

Reference throughout this specification to “one embodiment,” “certainembodiments,” “one or more embodiments” or “an embodiment” means that aparticular feature, structure, material, or characteristic described inconnection with the embodiment is included in at least one embodiment ofthe disclosure. Thus, the appearances of the phrases such as “in one ormore embodiments,” “in certain embodiments,” “in one embodiment” or “inan embodiment” in various places throughout this specification are notnecessarily referring to the same embodiment of the disclosure.Furthermore, particular features, structures, materials, orcharacteristics may be combined in any suitable manner in one or moreembodiments.

Although the disclosure herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent disclosure. It will be apparent to those skilled in the art thatvarious modifications and variations can be made to the method andapparatus of the present disclosure without departing from the spiritand scope of the disclosure. Thus, it is intended that the presentdisclosure include modifications and variations that are within thescope of the appended claims and their equivalents.

What is claimed is:
 1. A physical vapor deposition (PVD) chambercomprising: a plurality of cathode assemblies including a first cathodeassembly including a first backing plate to support a first targetduring a sputtering process and a second cathode assembly including asecond backing plate configured to support a second target during asputtering process; an upper shield below the plurality of cathodeassemblies having a first shield hole having a diameter and positionedon the upper shield to expose the first cathode assembly and a secondshield hole having a diameter and positioned on the upper shield toexpose the second cathode assembly, the upper shield having a flatinside surface, except for a region between the first shield hole andthe second shield hole; and a raised area in the region between thefirst shield hole and the second shield hole, the raised area having aheight greater than one centimeter from the flat inside surface andhaving a length greater than the diameter of the first shield hole andthe diameter of the second shield hole, wherein the PVD chamber isconfigured to alternately sputter material from the first target and thesecond target without rotating the upper shield.
 2. The PVD chamber ofclaim 1, wherein the raised area has a height sufficient so that duringa sputtering process, the raised area prevents material sputtered fromthe first target from being deposited on the second target and toprevent material sputtered from the second target from being depositedon the first target.
 3. The PVD chamber of claim 1, wherein the firstcathode assembly comprises a first magnet spaced apart from the firstbacking plate at a first distance and the second cathode assemblycomprises a second magnet spaced apart from the second backing plate ata second distance, wherein the first magnet and the second magnet aremovable such that the first distance can be varied and the seconddistance can be varied.
 4. The PVD chamber of claim 3, wherein the firstmagnet and second magnet are configured to be moved to decrease thefirst distance and the second distance to increase magnetic fieldstrength produced by the first magnet and the second magnet and toincrease the first distance and the second distance to decrease magneticfield strength produced by the first magnet and the second magnet. 5.The PVD chamber of claim 3, wherein the first target comprises amolybdenum target and the second target comprises a silicon target, thePVD chamber further comprising a third cathode assembly including athird backing plate to support a third target during a sputteringprocess and a fourth cathode assembly including a fourth backing plateconfigured to support a fourth target.
 6. The PVD chamber of claim 5,where the third target comprises a dummy target and the fourth targetcomprises a dummy target.
 7. The PVD chamber of claim 6, wherein thirdtarget and the fourth target are positioned with respect to the firsttarget and second target so that when the upper shield is in a firstposition, the first target is exposed through the first shield hole andthe second target is exposed through the second shield hole, and thethird target and fourth target are covered by the upper shield, and whenthe upper shield is rotated to a second position, the fourth target isexposed through the second shield hole and the second target is exposedthrough the first shield hole.
 8. The PVD chamber of claim 7, whereinwhen the upper shield is rotated to a third position, the first targetis exposed through the second shield hole and the fourth target isexposed through the first shield hole.
 9. A physical vapor deposition(PVD) chamber comprising: a plurality cathode assemblies including afirst cathode assembly including a first backing plate supporting afirst target comprising molybdenum and a second cathode assemblyincluding a second backing plate supporting a second target comprisingsilicon, a third cathode assembly including a third backing platesupporting a third target comprising a dummy material, and a fourthcathode assembly including a fourth backing plate supporting a fourthtarget comprising a dummy material; an upper shield below the pluralityof cathode assemblies having a first shield hole having a diameter andpositioned on the upper shield to expose the first target and a secondshield hole having a diameter and positioned on the upper shield toexpose the second target, the upper shield having a flat surface, exceptfor a region between the first shield hole and the second shield hole,the upper shield configured to permit molybdenum and silicon material tobe alternately sputtered from the first target and the second targetrespectively without rotating the upper shield; and a raised area in theregion between the first shield hole and the second shield hole, theraised area having a height greater than one centimeter and having alength greater than the diameter of the first shield hole and the secondshield hole, wherein the upper shield is rotatable to allow one of thefirst shield hole and the second shield hole to expose the first targetand one of third target and the fourth target.
 10. The PVD chamber ofclaim 9, wherein each of the first cathode assembly, the second cathodeassembly, third cathode assembly and fourth cathode assembly comprise amagnet spaced apart from the first backing plate at a first distance,the second backing plate at a second distance, the third backing plateat a third distance and the fourth backing plate at a fourth distance,each of the magnets being movable to increase or decrease each of thefirst distance, the second distance, third distance or fourth distance.11. The PVD chamber of claim 10, wherein decreasing the first distance,the second distance, the third distance or the fourth distance increasesmagnetic field strength produced by the magnet, and increasing the firstdistance, the second distance, the third distance or the fourth distancedecreases magnetic field strength produced by the magnet.
 12. A methodof depositing alternating material layers in a physical vapor deposition(PVD) chamber comprising: placing a substrate in the PVD chambercomprising a plurality cathode assemblies including a first cathodeassembly including a first target comprising a first material and asecond cathode assembly including a second target comprising a secondmaterial different from the first material; disposing an upper shieldbelow the plurality of cathode assemblies, the upper shield having afirst shield hole having a diameter and positioned on the upper shieldto expose the first target and a second shield hole having a diameterand positioned on the upper shield to expose the second target, theupper shield further comprising a flat surface between the first shieldhole and the second shield hole and a raised area between the two of theshield holes having a length at least equal to the diameter of the firstshield hole and the second shield hole; and alternately sputteringmaterial from the first target and the second target without rotatingthe upper shield, wherein the raised area prevents the first materialfrom contaminating the second target and prevents the second materialfrom contaminating the first target.
 13. The method of claim 12, whereinthe chamber further comprises a third target comprising dummy materialand a fourth target comprising dummy material and wherein third targetand the fourth target are positioned with respect to the first targetand second target so that when the upper shield is in a first position,the first target is exposed through the first shield hole and the secondtarget is exposed through the second shield hole, and the third targetand fourth target are covered by the upper shield during depositingalternating material layers from the first target and the second target.14. The method of claim 13, further comprising cleaning first materialdeposited on the second target by applying a magnetic field to thesecond target that is greater than a magnetic field applied duringdepositing alternating material layers.
 15. The method of claim 14,further comprising cleaning second material deposited on the firsttarget by applying a magnetic field to the first target that is greaterthan a magnetic field applied during depositing alternating materiallayers.
 16. The method according to claim 14, further comprisingrotating the upper shield from the first position to a second positionprior to cleaning the first material from the second target, the fourthtarget is exposed through the second shield hole and the second targetis exposed through the first shield hole.
 17. The method according toclaim 16, further comprising rotating the upper shield from the secondposition to a third position so that the first target is exposed throughthe second shield hole and the fourth target is exposed through thefirst shield hole.
 18. The method according to claim 17, wherein thesubstrate comprises an extreme ultraviolet (EUV) mask blank.
 19. Themethod according to claim 18, wherein the first target materialcomprises molybdenum and the second target material comprises silicon.20. The method according to claim 19, further comprising depositingmultiple alternating materials layers comprising a first layercomprising molybdenum and a second layer comprising silicon.